1. Field of the Invention
The present invention relates to a high-speed WPAN (Wireless Personal Area Network) based on the IEEE (Institute of Electrical and Electronics Engineers) 802.15.3 standard using an UWB (Ultra Wide Band) frequency. More particularly, the present invention relates to a high-speed WPAN adapted for supporting communication between devices located in different piconets.
2. Description of the Related Art
Typically, wireless communication technologies using an UWB (Ultra Wide Band) transmission frequency can typically communicate between devices at a distance of 10 m˜1 km with use of a frequency band of 3.1 GHz˜10.6 GHz. The wireless communication technologies using the UWB have been used for military wireless communication technologies in the US D.O.D. (United States-Department of Defense) during the last 40 years, and were recently opened to the private sector by the FCC (Federal Communications Commission).
The wireless communication technologies using the UWB are very high-speed wireless data transmission technologies based on a UWB of several GHz, and have characteristics of a high data rate (e.g., 500 Mbps˜1 Gbps) and utilize very low levels of electric power (e.g., 1/100 of the electric power required for a mobile phone and a wireless LAN (Local Area Network)) in comparison with existing IEEE 802.11 (Institute of Electrical and Electronics Engineers) and Bluetooth technologies. The applications of wireless communication technologies using the UWB are varied, and include fields associated with personal area networks (PANs) for connecting computer systems, peripheral devices and home appliances to a very high-speed wireless Internet in a local area (e.g., an average distance of 10 m˜20 m and a maximum distance of 100 m), “through-the-wall” radars for detection of objects behind walls of buildings, high-precision positioning and geolocation systems, vehicle collision avoidance sensors, mine detectors, loss prevention systems, detectors for detecting objects inside human bodies, etc.
IEEE 802.15.3 high-speed WPAN (Wireless Personal Area Network) standards are proposed in terms of the wireless communication technologies using the UWB frequencies. In terms of IEEE 802 working groups before IEEE 802.15.3 is described, IEEE 802.15.1 is a working group for standardizing Bluetooth specifications, and IEEE 802.11 is a working group for standardizing wireless LANs.
As a well-known PAN (Personal Area Network) technology, Bluetooth has now reached the stage of commercialization. The Bluetooth technology has been recently adopted and commercialized in an ever-increasing list of products. IEEE 802.11 wireless LANs have been completely standardized. The above-described networks mostly use a frequency band of 2.4 GHz (e.g., an ISM (Industrial, Scientific and Medical) radio band), and are used as a PAN solution within the communication distance of 10 m.
IEEE 802.15.3 working groups include TG1 (Task Group 1), TG2 and TG3. The TG1 is currently conducting the standardization of Bluetooth specifications. The TG2 is analyzing technologies for facilitating coexistence of Bluetooth products and existing wireless LANs. As a group for standardizing high-data-rate PAN solutions, the TG3 studies a transmission scheme for implementing a data rate of 55 Mbps or above.
FIG. 1 is a view illustrating an exemplary piconet formed between devices located in an IEEE 802.15.3 high-speed WPAN.
As shown in FIG. 1, the piconet forming the high-speed WPAN includes a plurality of communication devices 10, 12, 14, 16 and 18. The device 10 acts as a PNC (Piconet Coordinator). The PNC device 10 manages timeslots necessary for communication of the devices located in its own piconet using beacon messages for synchronizing its own device with the devices 12, 14, 16 and 18 connected thereto. Furthermore, the PNC device 10 further performs an operation for controlling QoS (Quality of Service), a power save mode and a piconet access.
An IEEE 802.15.3 device capable of acting as the PNC can form one single piconet. A procedure for forming a piconet by means of a device with the capability of the PNC is as follows.
In order to initiate the operation of the piconet, the PNC device 10 searches for at least one channel selected from all of the channels not currently in use, and broadcasts a beacon frame through the selected channel. In response to the receipt of the beacon frame broadcast by PNC device 10, the devices 12, 14, 16 and 18 carry out a communication channel setup operation. At this time, the PNC device 10 allocates IDs (Identifiers or Identities) corresponding to the devices 12, 14, 16 and 18.
An arbitrary device performs an association procedure when desiring to join an already-formed piconet. In other words, the arbitrary device moves to the already-formed piconet from an external area by requesting that the PNC device 10 connect its own device to the already-formed piconet. In response to the request, the PNC device 10 allocates a single device ID usable in the piconet from which the arbitrary device makes the request.
Throughout the association procedure, the piconet is formed as shown in FIG. 1. When one of the devices 12, 14, 16 and 18, (except for the PNC device 10), desires to transmit data, the particular device or devices 12, 14, 16 and 18 request that the PNC device 10 transmit data, by performing “a data transmission request.” In response to the data transmission requests from the one or even all of the devices 12, 14, 16 and 18, the PNC device 10 allocates timeslots for enabling data communications to the devices 12, 14, 16 and 18. Upon allocating the timeslots to the device 12, 14, 16 and 18, the PNC device 10 transmits the allocated timeslots to the devices by using the beacon frame. Consequently, each of the devices 12, 14, 16 and 18, after being informed of their allocated time slots contained in the beacon frame, performs a data transmission operation during their allocated timeslot.
On the other hand, should an arbitrary device desire to terminate a communication operation within the piconet, or where the PNC device 10 desires to release a communication connection with the arbitrary device, a disassociation procedure between the PNC device 10 and the arbitrary device is performed. Thus, the PNC device 10 deletes information of the registered arbitrary device through the piconet disassociation procedure.
The piconet formed between the PNC device 10 and the devices 12, 14, 16 and 18 is classified as both an independent piconet capable of independently allocating timeslots to the devices that are located within the piconet, and a dependent piconet capable of distributing and allocating timeslots provided from a PNC device located outside the piconet to the devices located within the piconet. If at least one dependent piconet is newly generated into an independent piconet, then the independent piconet is referred to as a “parent piconet”, and the newly generated dependent piconet is referred to as a “child piconet” or “neighbor piconet”. That is, the independent piconet becomes the parent piconet, and the dependent piconet becomes the child piconet. In this case, the child piconet (or dependent piconet) uses a common channel provided from the PNC device located in the parent piconet.
FIG. 2 is an example of both an independent piconet and a dependent piconet, wherein the dependent piconet is formed within the independent piconet. An already-formed piconet becomes a parent piconet 30. A PNC device of the parent piconet 30 is referred to as a P-PNC device 32. Any device with the capability of a PNC device except for the P-PNC device 32 among the devices 22, 24 and 34 can form a child piconet 20.
The P-PNC device 32 allocates timeslots to the C-PNC device 22 and the device 34 forming a child piconet associated with the parent piconet 30 through the transmission of beacon frames containing the allocated timeslots. A device performing a PNC function in the child piconet 20 is referred to as the C-PNC device 22. The C-PNC device 22 can form the child piconet 20, and manages and controls the device 24 forming the child piconet 20. Furthermore, communications within the child piconet 20 can be performed only between the devices 22 and 24 forming the child piconet 20. Thus, the C-PNC device 22 manages and controls the child piconet 20, and is also one member forming the parent piconet 30. The C-PNC device 22 can communicate with the devices 32 and 34 located in the parent piconet 30.
The operation of a neighboring piconet (not shown) is identical to that of the child piconet 20. An N-PNC (Neighbor PNC) device controls devices forming the neighbor piconet is not a member of the parent piconet. Thus, the N-PNC device cannot communicate with the devices of the parent piconet 30 unlike the C-PNC device 22.
FIG. 3 illustrates the configuration of conventional parent and child piconets. A P-PNC (Parent Piconet Coordinator) device 62 manages a C-PNC (Child Piconet Coordinator) device 42 and a device-G 64 that are both members of the parent piconet 60. Furthermore, the C-PNC device 42 manages a device-A 46 and a device-B 48 that are both members of the child piconet 40.
The P-PNC device 62 generates mapping information containing a MAC (Media Access Control) address (64 bits) and a device ID (8 bits) using information transmitted from each of the devices 42 and 64, stores the generated mapping information in a P-MIB (Parent Piconet Management Information Base) 63, and manages the stored generated mapping information. The P-PNC device 62 broadcasts the information of the devices 42 and 64 registered in the parent piconet 60 using beacon frames. Only the devices 42, 62 and 64 that are registered in the parent piconet 60 can receive the beacon frames broadcast by the P-PNC device 62. The devices 42 and 64, which are located in the parent piconet 60, generate mapping information associated with the devices 42 and 64 using information of the beacon frames transmitted from the P-PNC device 62, store the mapping information in P-MIBs 44 and 65, and manage the stored generated mapping information.
When the device G-64 desires to transmit data to the P-PNC device 62, the first step is a searche for the mapping information from the P-MIB 65 that refers to an ID of the P-PNC device 62. Subsequently the data is transmitted to the P-PNC device 62. On the other hand, the C-PNC device 42 managing and controlling the child piconet 40 broadcasts information of the device-A 46 and the device-B 48 located in the child piconet 40. The broadcast information is not that registered as the mapping information stored in a C-MIB (Child Piconet Management Information Base) 43. Here, the devices 46 and 48 of the child piconet 40 that are registered in the C-PNC device 42 can only receive the beacon frames.
The device-A 46 and the device-B 48 store, in the C-MIBs 47 and 49, the mapping information associated with the devices registered in the C-MIB 43 of the C-PNC device 42 using the beacon frame information broadcast from the C-PNC device 42, and manages the stored mapping information. Thus, when desiring to transmit data to the device-B 48, the device-A 46 searches for the mapping information stored in the C-MIB 47, refers to ID information of the device-B 48, and transmits the data to the device-B 48.
FIG. 4 is a table illustrating an example of mapping information stored in MIBs. Mapping information stored in the P-MIBs 63, 65 and 44 of the devices 62, 64 and 42 located in the parent piconet 60 contains information associated with device addresses, device IDs and piconet IDs for the devices 62, 64 and 42 located in the parent piconet 60.
Furthermore, mapping information stored in the C-MIBs 43, 47 and 49 of the devices 42, 46 and 48 located in the child piconet 40 contains information associated with device addresses, device IDs and piconet IDs for the devices 42, 46 and 48 located in the child piconet 40.
Since the devices located in the same piconet share the mapping information as described above, the devices located in the same piconet can perform mutual communication with each other.
On the other hand, when desiring to transmit data to the device-G 64 located in the parent piconet 60, the device-A 46 located in the child piconet 40 searches for mapping information from the C-MIB 47 to detect ID information of the device-G 64. However, the ID information of the device-G 64 is not contained in the C-MIB 47. Thus, the device-A 46 cannot transmit corresponding data to the device-G 64. Since the parent piconet 60 and the child piconet 40 are independently configured networks, there is a problem in that communications cannot be performed between the devices located in the different piconets.
In other words, the conventional high-speed WPAN technology can only support communication between the devices located in one piconet, but cannot support communication between the different devices registered in different piconets. Furthermore, there is another problem in that a communication distance between the devices is limited to within a short communication radius of 10 m since the conventional high-speed W PAN technology uses the UWB signal.
Since the PNC device of the child piconet is a member of the parent piconet when the parent and child piconets are formed, the PNC device can communicate with other devices located in the parent piconet. However, other devices except for the PNC device located in the child piconet cannot communicate with devices located in the parent piconet.